T568A / T568B

T568A and T568B differ only in the position of the orange and green wire pairs at the RJ45 connection. Electrically, both standards deliver identical performance — the distinction is purely in the physical wire pair assignment.

T568B is the standard for commercial office installations in the United States. The most important requirement is consistency — every outlet, patch panel, and patch cord in a facility must use the same standard.

Using different wiring standards at the two ends of the same cable segment creates a crossover cable — which will prevent normal network devices from communicating. Modern gigabit switches with auto-MDI/MDI-X detection can compensate, but consistent pinout standards eliminate this variable entirely.